thanks for the replies.
I'd wondered if it was a post code checker error, and maybe because no-one in the close does have a BT line. To clarify, we've all moved (independently and over the years) from BT to other providers for telephone and ADSL, there's a few on Sky (me included) and Tiscali but no BT. We don't have the option of CATV here.
As suggested I've just tried TalkTalk (who I didn't realise now offer FTTC) checker with a neighbours number (who is on TalkTalk) and that's a positive. I enter my number (Sky) and I'm asked for my postcode, which returns a negative.
So that does suggest that it's an error on the database, so I either now wait for Sky to offer FTTC, or try calling BT or Talk Talk again. Last time I tried BT, I couldn't get past the Agent in the Call Centre, as she insisted that FTTC was not available, presumably because she was using the same database.